Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to contextual awareness using relative positions of mobile devices.
Background
Numerous systems and methods exist for tracking the location of users. Such tracking may be performed to support context-aware applications, to provide location-based services, or for a variety of other reasons. Tracking of users is often performed by tracking the location of a device or object uniquely associated with the user. For example, numerous mobile devices carried by users today include technology that enables the location of such devices to be determined with varying degrees of accuracy. Such technology may include but is not limited to a Satellite Positioning System (SPS) (e.g., Global Positioning System (GPS) technology), (Wireless Local Area Network)WLAN technology, cellular telephony technology and Bluetooth technology. Information obtained from the mobile devices may include actual location information. For example, the location information may be based on built-in GPS capability, or relative location information, such as proximity to other mobile devices, beacons, or other identifiable objects or locations.
Positioning methods can determine a location of a target device from measurements by the target device of known external signal sources, such as SPS satellites or network base stations. In addition, measurements by network entities (e.g., base stations) of signals from the target device may also help determine the location of the target device. These measurements may enable the determination of a current, absolute location of the target device, for example, its precise latitude, longitude and altitude.
If a target device is unable to measure signals from external sources, and network entities are unable to measure enough signals from the target device, it may not be possible to obtain the location of the target device, and/or to obtain the location within a desired response time. Such cases may occur when there are physical obstructions between the target device and the external signal sources and/or network entities, for example. The inability to measure signals can occur when a target device is inside a building or tunnel, outside in a dense urban environment, or very distant from terrestrial external radio sources and network entities.